/Engine/Source/Editor/UnrealEd/Classes/Editor/EditorEngine.h
Sets and clears all Bsp node flags. Affects all nodes, even ones that don't really exist.
virtual void polySetAndClearPolyFlags ( [UModel](API\Runtime\Engine\UModel) * Model, uint32 SetBits, uint32 ClearBits, bool SelectedOnly, bool UpdateBrush )